Brake



Aug- 18, 193.6. c'. A. SAWTELLE '2,051,275

BRAKE 2 Sheets-Sheet 1 Filed Oct. 16, 1953 Aug. 18, 1936. c. A. sAwTELLE BRAKE 2 Sheets-Sheet 2 Filed Oct. 16, 1955 |||||l|1ll Ilnlllll Patented Aug. 18, 1936 UNITED STATE-s I BRAKE charles A. sawtelle, Detroit, Mich., assignor to S. & D. Engineering Company, Detroit, Mich., a corporation of Michigan Application vOctober 16, 1933, Serial No. 693,731

17 Claims.

This invention relates to brakes, and particularly vehicle brakes.

An object of the invention isgto'provide for applying a brake, through the usual range of selective pressures, with considerably less muscular effort than is now generally required, by utilizing a predetermined fraction of the torque induced in the brake band or shoe by the originally applied force to automatically build up said force. T' Another object is to utilize,'as above described, a fraction of the torque initially imposed upon a band or shoe, to automatically'build up the initially applied pressure, and to eliminate any uncontrolled augmentation of brakerpressure due l to the grabbing orwr'app'ingv action of the band or shoe.

Still another object is to provide improved means, accessible from the exterior of a brake drum, for adjusting a brake bandY (or other friction element) within the drum to compensate for wear.

A further object is to oppose a yieldable resistance of predetermined magnitude to the torque thrust of a brake band or the like, and to l5 utilize the resulting reaction upon the trailing portion of the band to compensate for the inherent tendency of the leadi-ng portion of the band to exercise a pressure superior to that of the trailing portion.

0 A still further object is to'c'onstruct the actuating mechanism for a 'brake band or'shoe largely of sheet metal stampings and thus promote low cost production and a compact assembly.

These and various other objects the invention attains by the construction hereinafter described, and illustrated in the accompanying drawings,

wherein:

Fig. 1 is a view in sectional elevation of the 0 improved brake, the plane of section being a rotational one, indicated bythe line l-I o'f Fig. 3.

Fig. 2 is a vertical cross sectional View of the brake, taken upon the linel 27-1-2 vof. Fig. l.

A Fig. 3' is a top plan View of the brake, with i5 the drum broken away to disclose interior mechanism.

Fig. 4 is a bottom plan view of the brake band, same being partly broken away to disclose interior mechanism.

Fig. 5 is a radial sectional View of the brake, taken on the line 5d-5 of Fig. 1, and disclosing certain features of the control mechanism.

Fig. 6 is a fragmentary vertical section taken 55 upon the line'B-S of. Fig. vLand showing a pro- (Cl. 18S- 78) vision for maintaining a. desired adjustment for wear. Y

Fig. '7 is a fragmentary elevationalrview, showing particularly a pair of links formed integrally with arms projecting toward each other', this vl'i view omitting other parts which, in` Fig. 1, lar'gely conceal said links and arms.

In these views, the reference character I designates a brake drum attached at one side to a wheel la, and closed at its other side by a dust 1"'0 plate Ib, suitably restrained from rotation, as by attachment to an axle housing 2. A suitable friction means such asl abrake band 3 o'f the usual exible type is interiorly engageable with said drum, and is equipped withv the usual re- 1:5 newable lining strip 4. The ends of saidv band are spaced apart adequately to provide for location of a suitable actuating mechanism between said ends.

Within said drum, and substantially in its 20 central plane of rotation, is mounted a heavy sheet-metal plate 5 tocarry said actuatingmechanism. Said plate, in the illustrated embodiment of the invention, is secured to the axle housing 2', preferably by bolts l6 engaging a ilange 'l exte- .2'5 riorly formed on said housing.

The upper end portion of theplate 5V lies between and adjacent to the ends of the band and is overlapped by brackets 8 and 8a', projecting toward each other from the band extremities. Each of the latter rigidly Vcarries two pairs of saidV brackets, said pairs extending at opposite sides of the plate 5, and being preferably each formed as a sheet-metal stamping.

Engaged between each pairv of the brackets 8 and pivoted thereto by a pin 9, is the upwardly projecting arm yof a .stamped sl'ieet-metalY Vbell crank l0, the otherarm of which projects toward the vertical` axial plane of the drum.y .The two bell cranks I0 thus connected to the normally 40 trailing band extremity are pivotedA at their apices upon a pin I'I, which is in turn journaled in the lower ends of a pair .of stamped sheet-metal links -l2, occupying a substantially radial relation to the drum. The latter lie against oppo- `sitefaceszof the `plate andareijointly pivoted,-at their upper ends uponl said plateby--a .pin i3. Similar vbell cranks 1I lla', disposed reversely ato' the bell cranks I0 compriseiupwar'dl-yproiiecting'arms connected :at `9a Lto the normally leading end of the band andhorizontally 'pro'jectingarms iterminaliy overlapping the''Correspfinding,farmsI of thebell cranks l0. 'The bellacrankslllw-.are pivoted atftheir apices, Acorrespondingly'to the `bell 55 Y:cranks I on pins VIlan journaled inthe lower Y endsV of radialV sheet-metal links 12a, which are pivoted at Vtheir upper ends'on the plate 5 by a cranks Vare pivotally interconnected by trunnions I4 projecting integrally from opposite facesY of a' 1 rectangular nut I5, each vtiunnionY being engaged Ybyoverlapping arms of two Vbell cranks YIIl and Illa..

. v Y For actuating the bell cranks in unison, a verti- Y cal stem` IB is threadedat its lower end into theV nut VI5anfi a yokeY I'I formed upon a-rock-shaft I8is engaged between a pair of'annular'flan'ges VI9 and 2G carried by the upper portion ofV said stem. To accommodate said stem and the nut I 5, Van opening 2I isformed in the upper portion of the 'plate 5, and preferably has Va lateral extentV adequate toaccommodate the pins II and Ha,

.thus affording the latterfa limited movement in VYtherotatio nal plane of the drum.

YAbo ve-the.opening 2 I,.there is 'welded or other- Ywise rigidlysecured to the plate 5.a relatively small plate 22, elongated.circumferentially of the drum.V The mid portion Vofsaid small plateand an opposed Yportion vZil'of V:the plate 5 are reversely VVlaterally 'offset to forman approximately rec,-V tangular chamber24, receiving the flanked upper Vend lofthe stem I5. VAlso the spaced walls Vof said chamberjournal the rock-shaft YI8 and'lmaintain Y engagement ofthe yoke I 1 between the flanges I9 Vand 20 within saidchamber. Said rock-shaft extends exteriorly of the drum :through the dustVY plate Ib,'and ca rries any suitable actuating elenient, exemplified by the arm 25.A Said arm may be connected by a pullrod a and othersuitable mechanism to va control pedal (notshown). Preferably aA coiled spring 26 extends from said arm to the outer margink of the dust plate (or some Vother .fixed support), establishing Ythe illustrated normal positions of lthe shaft I8, stern.V lli,V andV yoke 'IIjand bell cranks I0 and 10a, effecting retraction of the brake band. Clockwise actuation of the 'e rock-shaftY (seeV Fig.. 1) overcomes `the Y spring 25, raises said'stern, and acts through the Y 'f VThe-links I2 and'IZa are Vrespectively integrally bell Vcranks to expand the band against the drum.

formed witharms v2,'I *and 21a, terminally projecting beneath the 'flange I9 for the purpose of utilizing Ya fractionV ofthe torque v.pedally impressed on the brake band, to automatically Vine` creaseVV the pressure appliedby'the band. This Vfeaturefwill Vpresently be explained indetail.

' To'eiect wear-compensating,adjustment of the described' mechanism, aworm 28, fast on an adjustingV shaft-29.inthe chamber 24, is meshed with gear teeth peripherally Vformed on the flange 19; saidshaft ,rjourna1edzin thewaus z2 and z3 Yof said chamber, has an en'd portion projecting exteriorly ofthe drurri'through the dust plateV Ib.

'i r Saidendportionis Vsquared-to non-rotatively and rigidly mount a sheet metal spring :3I terminally urged against thefdust plate and Vterminally bent to 'an 'approximate V .formfor Vengagement in an indentation" 33 in the dust plate, to restrain the adjusting shaft from rotation. VA stressing of said springaway from the dust plate allows rotative Vactuation ofthe adjusting shaftV and stem I6, such as to screw the latter increasingly into the nutV I5. Since under these conditions the 'stemY is restrained by the yoke AI'I fromvertical actuation, the described rotation .of Ythe stem Yelevates the nut I5, thereby rocking the two Ybell-cranksin a direction .to increasingly spaceY the brake'band extremities. Y f f f l Fromthe Ylower end of the plate 5, atongue 34 projectsdownwardly toV engage freely in a Yslot formed centrally in a leaf/springU v35,*brid'ge'd across the lower portion of the brake band, and 4 terminally riveted to the latter. Said Vspring has a shallow V-form, its halves Vupwardly diverging to encounter the band in a predetermined angular relation, adapting said spring to properly guide VtheV band in its expansion and contraction. Said spring furthermore materi'ally'as'sists` in holding the band'centered in the drum, with respectboth to the side walls and periphery of said drum-' Said central slot in the leaf spring'35has exten-V sions. at each side of the vt ongu'e,34, accommodating a pair'of coiled springs 36, held vrin'place at their outer endsby lugs Y3'I'integ'ral.with'said leaf spring and attheirinnerfendsby a pair of Y1ugs38, integral withfthe tongue 34'. A pair of A cotter pins V39 orV the like Vare passed through Y,

the tongue'34, aboverandbelow the spring 35, restraining theV mid portion of saidcsprng from vertical movement whileallowing it an approxi-V mately circumferential travel.

In applying the described brake, the rock-shaft I8 is actuated (through theusual footjpedalVpull rods and levers, not shown) in a-direction toelevate the yoke Il, acting through the latter vto liftVV j the stern I 6. Resultant reverse rocking of the paired bell cranks I0 and Illa. spreads apart the brake band'extremties, and expands the band Vagainst the drum. The latter, if rotating ina normal direction, imposes` a torque onV the band,

acting as indicated bythe arrow4|l in Fig. 1.

This torque is resisted by the pins 9a at the leading Vend (or heel) of the band andtends through said pin to rock the bell-cranks IIla in a counter-clockwise direction (see Fig. 1) Suchtendency is,

however, negatived by the pedal-,imposed force,

holding the stern` I6 raised. Consequently, the

bell-cranks-Ia act as substantially Vrigid members in receivingY said torque thrust, and transmit such thrust to the-trunnions I4 and thence to the bell-cranks I0 and lower end "of `the stem I6, so

as Vto eiect alimited swingingfof the links I2and I2aV and stem I 6 in the approximate direction of drum rotation. The arms 21a are vthus swung upwardly at their free ends, and deliver their upthrust to the stem I6 through the flange `2li. Thus, theV pedal-induced braking effort `is Yautomatically augmented` by a ltorque factor, .applied through the arms` 21a, Yand constituting a fraction of the brakeeband torque established bythe ratio between the' effective length of vthe links I2a., and that of the arms 21(17asY measured from the pin I3a. By ,selecting a desired ratio forthis controlling` fraction, the brake-band'torque may be utilized` to Va Ypredetermined extent in auto-V matically increasing any muscularly applied braking effort. A w Y' Y An important advantage accruing fromV the use'ofi the-described mechanism, asa means for expanding the brake band, lies-in the reaction 1 of the paired bell-cranks upon eachother to pre-VV Vent the'band from exertingran "uncontrollable wrapping pressure upon the drum@ Thus, ifr the drum is rotating in its usual direction, as in-Y ,dicated by the arrow, when the brake is applied,

there is a ktendency originating at the trailing or toe end of the band to expand the latter increasingly due to torque imposed on said end. The torque thrust imposed on the pin Sa by the wrapping effect acts, however, through both bellcranks to exert an equivalent upwrapping eiect on the trailing or toe end of the band, whereby Wrapping or grabbing is effectively controlled.

It will be noted that the horizontal arm of the bell-crank lea. is vslightly longer .than that of the bell crank IB, thus affording the former a slight mechanical advantage in acting on the latter, to more completely and readily overcome wrapping effects.

It is also to be noted that the arms 21 jointly form a stop, positively limiting down travel of the stem I6 and thus limiting retraction of the band. The links carrying said arms cannot swing apart responsive to engagement of said arms by the flange 20, since said links are tied together by the lower arms of the paired bell-cranks.

The purpose of the springs 35 is to counteract the tendency of the leading portion of the brake band, for either direction of rotation of the drum, to engage the latter under greater pressure than the trailing portion. This tendency is objectionable in that it results in a wearing out of the normally leading portion of the brake lining in ad- Vance of the trailing portion thereof. The illustrated construction causes the arm 35 to act compressively upon one or other of the springs 35 when the drum is imposing torque'upon the band, with the result that the spring so compressed increases the braking pressure applied to the trailing portion so as to overcome or at least reduce, the discrepancy which would otherwise arise between pressures acting in the leading and trailing portions of the band.

It is important to note that the torque-induced increase in the initially applied braking force is not merely the reaction of a master shoe or band on a servo shoe or band, but involves utilization of a torque arising from an initial application of a friction applying member tosubject the same member to a considerably increased braking force.

Furthermore, utilization of torque in the disclosed brake for augmenting the initially applied force does not entail any greater circumferential travel of the friction-applying member than is required to render said member properly responsive to the initially applied control.

While it is apparent that the illustrated embodirnent of my invention is well calculated to adequately fulll the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

What I claim is:

1. A brake comprising a brake drum, a dust plate forming a closure for one side of the drum, friction means interiorly engageable with said drum, a control member within the drum movable to actuate said friction means, an adjusting shaft extending exteriorly of the drum through said dust plate, an actuating connection from said shaft to said control member, a handle carried by said shaft exteriorly adjacent to the dust plate and adapted to interlock with the dust plate, and a spring normally urging said handle into interlocking engagement with the dust plate.

2. A brake comprising a brake drum, friction means interiorly engageable with said drum, a control member for said friction means, a link mounted substantially radially within the drum and adapted to swing about its outer extremity, a

'member vpivoted upon the inner extremity of said 'link and establishing an `actuating connection from said kcontrol member to said friction means, and an arm carried by said link, reacting upon .said

control member responsive to torque in the friction means, to automatically increase the applied braking effort. f

3. A brake comprising a brake drum, friction means interiorly engageable with said drum, a radially movable control member for said friction means,` a pivotal actuating connection between. said control member and the friction means, a link pivotally mounting said actuating connection and angularly actuable responsive to the torque of the friction means, and an element carried by said link, reacting upon said control member responsive to torque in said friction means to automatically increase the applied brak#- ing effort.

4. A brake comprising a brake drum, friction means interiorly engageable with said drum and having spaced ends, a control member positioned between said ends and movable substantially radially, a pair of actuating connections to said spaced ends from said control -member, a pair of substantially radial links each pivotally Ymounting one of said actuating connections, and a pair of elements respectively carried by said links reacting upon said control member responsive to torque in said friction meanato automatically increase the applied braking effort.

5. A brake comprising a brake drum, a brake' band interiorly engageable with said drum, a .leaf spring bridging the mid portion of the band, a xed support for the mid portion of said leaf spring, affording said spring a sliding'travel approximately circumferential to the drum, and means reacting between said support and the leaf spring at each Vside of the support,.resisting the torque thrust of the band.

6. A Ybrake comprising a brake drum, friction means interiorly engageable with the drum and comprising spaced ends, a pair of pivotally interconnected actuating members connected to said ends, an actuating stem for such members engaging them at their interconnection, and circum- -ferentially spaced-elements for actuating the stern longitudinally thereof toapply the brake, and for actuating the stem longitudinally thereof in compensation for Wear of the friction means, the stem being engaged between said elements.

7. A brake comprising a brake drum, a brake band interiorly engageable with said drum, a leaf spring carried by and bridging the mid portion of the band and bent to diverge toward its ends from said mid portion, and a support fixed relative to the drum, and mounting the mid portion of the leaf spring for a sliding travel tangential to said support.

8. A brake comprising a brake drum, means within the drum expansible to frictionally engage the drum, a pair of copivotal levers, an actuating element operatively engaging both of said levers, an actuating connection from the levers to said means, and a support for said levers, disposed between the levers and formed with an opening receiving the actuating element, and xed as regards drum rotation.

9. A brake as set forth in claim 8, said actuating element being mounted on said support.

l0. A brake comprising a brake drum, means within the drum expansible to frictionally engage the drum, said means having ends spaced circumferentially of the drum, a sheet metal plate mounted within and fixed relatively to the drum,

Y "approximately in its mid plane ofY rotation, an

actuating element movable in said plane, and two pairs of levers operatively connecting said element to'said ends, the levers of each pair being coi 5 pivotal on the support, at opposite sides thereof.

1l. Afb'rake comprising a brake drum, means VWithin the drum expansible to frictionally engage the drum, saidvmeans having ends spaced cir- Y VcumferentiallyY of the drum, a sheet'metal plate mounted Within and iixed relatively to the drum, approximately in its mid plane'of rotation, mechanism for expanding Vsaid means mounted upon the plate at one side of the drum axis and operatively Vconnected to said ends, and, means carried by the plate at the opposite side of the drum axis Vand engaging said means remotely from itsends for guiding said means into and out of engagement with the drum. Y

i12. In a brake, the combination with'a'brake drum'and means within therdrum expansible to VYfrictionally Vengagethe drum, said means having ends spaced circumferentially of the drum, of al mechanism engaging such ends to expand the frictional'means including a nut, a substantially` radial stem threaded into`the nut, meansY for shifting the stem radially to apply the brake, and means for rotating the stem Vto compensatefor Wear'of thefriction means. 'j 13. A brake comprising a brake'Ydrum, means within `the drum expansible to frictionally engage the drum, said vmeans having ends Aspaced circumferentially of the drum, a pair of bell cranks,

actuatinglconnections from the bell cranks Vto said spaced ends, a'nut pivotally interconnecting therbell cranks, a stem having'a threaded portion engaging the nut, means for bodily moving the stem to rock the bell cranks and expand the Y frictionmeans, and means for rotating the stem f in the nut to vary the eiective'V length of Y the stem.

14. Ina brake, the combination with'a'brake drum, Vand means within the drum expansible to -frictionally engage the drum, said means having endsYs'paced circumferentially of Vthe drum, yof a mechanism engaging said spaced endsrfor ex- V fpanding the friction means includinga nut, a

stem threaded Vinto the Ynutrand formed with a toothed annular ange, 'a lever: engaging said flange to actuate the stem radially, and a gear engaging said flangerfor rotating the stem to vvary itsYeffective length. v I

15. A brake comprising, in combination, abrake drum,V an expansible and contractible band having a limited circumferential movement WithYre- Y spect to the drum, a pair of bell cranks pivotally connected to the band and to each other for operating the band, means for rockingf'the bell cranks, operating onvtheir .pivotal interconnection, a pair of links respectively pivotally mounting the respective bell cranks, and occupying an approximately radial relation to the drum, pivotal spect to the drum, a pair of bell cranks pivotallyY connected to therband and to each other for op- Y erating the band, means for rocking .the bell cranks, operating on their pivotal interconnection, individual pivotal supports ,Y for theY bell cranks, independently aiording them a limitedV travel approximately circumferential to the'drum,l

and means carried by said pivotal supports react-` ing upon said rocking means Vresponsiveto torque Y, Y

in said band to automatically augment the Vap'- plied brakingeifort. Y

17. Inabrake the combination with `arbrake drum and means within the drum expansible Vto frictionally engage the drum, said means having ends spacedcircumferentially of the drum,l of a. pair of bell cranks, actuating kconnections from the nell cranks to said spaced ends, a lever, an actuat- Y ing Yconnection from said lever to thebell cranks comprising av steml and a nut threaded on, the

stem, said stem and nut being relatively rotat- Y Y able to vary the effective length of the actuating A connection, and means operable from the drum exterior for relatively rotating the stem and nut.

`CHARLES; A. sAW'I'ErLE. 

